Expansion joints



1965} A. J. HIRST ETAL 3,165,986

EXPANSION JOINTS Filed March 9, 1961 United States Patent ice 3,165,986 Patented Jan. 19 1965 EXPANSION JOINTS Archie John Hirst and Kazimierz Siwek, Leicester, England, assignors to Metalastilr Limited, ileicester, England, a British company Filed Mar. 9, 1961, Ser. No. 94,477

Claims priority, application Great Britain, Mar. 22,

Claims. (Cl. 94-18) This invention relates to an expansion joint for accommodating the expansion of a pair of surfacing members separated by the joint, the joint bridging an expansion gap between the surfacing members. The surfacing members may, for example, be adjacent concrete road sections or a road section joining with a bridge surface, the joint in the latter case accommodating expansion and contractionof the bridge, and in the former case expansion and contraction of the concrete road sections, with change of ambient temperature.

According to the invention the expansion joint comprises a body of rubber or the like resilient material held in a state of compression between the surfacing members, said body having an upper surface substantially in the plane of the upper surfaces of the surfacing members and being so shaped in cross-section that the body tends to buckle downwardly under the compressive forces acting upon it, and support means under the body and supporting the body against downward buckling, the support means maintaining the upper surface of 'the body substantially in the plane of the upper surfaces of the surfacing members at least'within the normal range of ambient temperature conditions.

Preferably, the support means is adjustable by expansion of the surfacing members, to accommodate bulging of the under-surface of the rubber or like material body. According to a feature of the present invention, the support means supports the body at least in two planes one to each side of its mid longitudinal plane.

According to a further feature of the present invention, the depth of the rubber or like material body is constant over at least a latter part of the expansion range of the surfacing members, the support means then also supporting the body in its mid longitudinal plane.

According to a still further feature of the present invention, the support means is formed by a pair of comb structures each having a backbone member with projecting teeth, the comb structures being fixed one to each of the surfacing members with their'teeth interleaved and extending in opposite directions across the gap beneath the rubber or like material body, the teeth together defining a trough with inwardly and downwardly inclined sides which move away from one another upon expansion of the surfacing members, the inwardly and downwardly inclined sides of the trough supporting the rubber or like material body in planes one to each side of its mid longitudinal plane.

Where the support means is to support the rubber or like material body also in its mid longitudinal plane the bottom of the trough, according to a still further feature of the invention, supports the body in that plane when its depth in the plane is constant.

It will be appreciated that in addition to supporting the rubber or like material body against downward buckling, the support means also supports the body against downward deflection under loads applied to its upper surface. There is therefore an advantage to be obtained in supporting the body centrally of the gap between the surfacing members as well as to each side of the centre.

A specific embodiment of the present invention will erence to the accompanying drawings in which:

FIG. 1 is a cross-sectional plan on line 11 in FIG.

2 of an expansion joint accordingto the present invention', and

'FIG. 2 is a cross-section on line 22 in FIG. 1.

The drawings show the expansion joint between a pair of surfacing members which in the present example are respectively a concrete road section indicated 'at 10 and an adjacent concrete bridge-surfacing section indicated at 11. The expansion joint, which is generally indicated at 12, is positioned between the sections 10 and 11, the joint bridging an expansion gap 14 between the sections.

The gap 14 is formed between transverse cast-in channel section members 15' fixed to underlying structures 16, the members 15' supporting platform plates 17. The platform plates 17in turn support the expansion joint 12, the joint being secured to the platform plates (and the concrete decking) by studs 19 mounted on further plates 20 fixed to the structures 16. Y

The joint comprises a body of rubber 21 generally of flat strip form with a flat upper surface 22 and a convexly curved under surface 23. The rubber body 21 has at each of its longitudinal edges a bonded-on metal edge bar 24 which is generally of L-shaped cross-section so as to afford a flange 25 the bars 24shaving fiat inclined faces 25 to which the rubber is bonded. The flanges 25 also have inclined wedging faces 27 the purpose of which is hereinafter described.

A pair of cast iron comb structures 28, 29 having backbone members 3i? and 31 and projecting teeth 32and 33 are fixed. one to each of the platform plates 17, being drawn against the plates by nuts 35 threaded onto the studs 19. The nuts 35 are located in wells 36 in the backbone members. The teeth 32 and 33 are interleaved and extendin opposite directions across the gap 14 beneath the rubber body 21. The teeth have upper surfaces which over an intermediate part of their length, between their backbone'structure and their free ends, are flat and horizontally disposed so as to lie in a common plane. The remainder of the upper surfaces of the teeth are upwardly inclined, the upwardly inclined upper surface parts 41 of the'teeth of each comb structure towards the free ends of the teeth being concavely curved and lying in a common surface of revolution, these common surfaces being symmetrically arranged with respect to the mid longitudinal plane of the rubberbody. Between the flat horizontal disposed upper surface parts 40 of the teeth and the upwardly inclined upper surface parts 41 of the teeth the teeth have transitional concave upper surface parts 42 of greater curvature than the upper surface parts 41. It will be seen therefore that the teeth 32 and 33 togetherdefine a shallow trough with downwardly and inwardly inclined sides (constituted by the upper surface parts 41 of the teeth), which sides move away from one another upon expansionof the sections 10 and 11. This enlarges the trough to accommodate bulging of the under surface of the rubber body 21 consequent upon its compression due to the expansion of the sections as hereinafter more fully explained. g

The backbone members 30, 31 of the comb structures 28, 29 have upstanding flanges 45, the comb structures together defining a trough the side walls 46 of which are formed by the flanges 45 and which are equally downwardly and inwardly inclined. 'This trough has in addition a flat floor portion 47 adjacent each of its side walls 46 which floor portions are defined each by a part of one portions 47 by bolts 48 screwed into the backbone members. V

The bolts 48 pass through clamping plates49 and slots 50 in the flanges 25, the slots 50 being open ended and extending normal to the walls 46;

The rubber body 21Lhas longitudinally extending reperature at the time of assembly. The. comb structures are thenfixed imposition by means ofthe studs 19, this prior to the pouring of the adjacent endparts of the concrete sections 10, 11 which are then poured level with the upper edges of the flanges 45. The rubber body unit to-- gether with its edge bars is then placed in position in the trough formed by the comb structures. Initially the rubber body unit lodges across the top of this trough with the faces 27 engaging the wall faces 46. The bolts 48 are then inserted'and screwed down until the flanges come flat against the floor portions 47.

Wedging action between the faces 27 and the walls 46 forces theedge bars towards one another thereby compressing the rubber body.

The shape of the rubber body in cross-section is such that under the compressive forces actingupon it it tends to buckle downwardly. This effect is further enhanced by the inclined faces 26 which impart a component of the compressive forces to the rubber body in'the downward direction.

As finally located however the rubber body is supported against downward buckling by the teeth 32' and 33 which form support means under the rubber body. The teeth 32, 33 support the rubber body with its upper surface 22 in the plane of the upper surfaces of the sections 10 and 11. The joint as shown in the drawings is assumed to be in its condition in which the expansion gap 14 is at a mean dimension. The range of relative expansion between the sections 10 and 11 which is afforded by the joint is twice the dimension x shown'in'FIG. l. a The support afforded to the rubber body by the teeth 32, 33 is, for wider 'gap dimensions, in two planes in the present example, namely the planes of the reinforcing rods 51 one to each side of themid longitudinal plane-52 of the body, the body in its mid longitudinal plane remaining clear of the horizontal surface parts 40 of the teeth until the gap 14'has been narrowed; by expansion of the sections 10 and 11 to its mean dimension.

Considering the sequence of events consequent upon expansion of the sections 10 and 11 narrowing the 'expansion gap 14 from its widest dimension, the rubber body is further compressed and its tendency to buckle downwardly 'still further increased. Furthermore there is a change of shape of its section due to the further compression resulting in a flow of rubber from one region'to another. This flow of rubber, and the consequent change to cross-sectional shape causes a general downward bulging of the under surface 23, the bulging of the under surface being permitted so as to prevent or substantially prevent change of shape of the upper surface 22.

The downward bulging of the body, in theregions of the rods 51, is accommodated by the movement of the teeth 32 and 33 which takes place upon the expansion of the sections, the inclined surface parts 41 sliding across the rods so that, relatively to the surface parts 41, the rods slide down the inclines they being maintained thereagainst by the buckling tendency. 7

Also; the rubber body begins to bulge on its underside between the rods 51 so as to form a longitudinally extending localised bulge 54 which finally comes into contact with the horizontal surface parts 40 of the teeth.

' mension of the gap 14.

, bring the surface parts 40 into the plane 52.

FIG. 2 shows the condition in which the rubber body 'first contacts the horizontal surface parts 40 along a line in the mid longitudinal plane 52. At this condition the movement of the teeth 32 has been suflicient to The inclination of the surface parts41 and 42 is so chosen that after the localised bulge 54 comes into contact with the horizontal surface parts 40, bulging of the rubber in the regions of the rods 51 and to each side of the plane 52 upon further expansion movement of the sections 10 and 11 is permitted to the extent required to absorb the consequentrubber flow, the rods 51 remaining always in contact with the surface parts 41 and the depth of the rubber body in the plane 52 remaining thereafter, constant; p

Once the rubber body has come into contact. with the horizontal surface parts 42 of the rubber body is supported in the centre as well as inthe planesvof the reinforcing rods. V

The reinforcing rods distribute the buckling load, and applied loads on the rubber body, across the surfaces of the teeth and prevent bulging of the rubber into the.

spaces between the upwardly inclined parts of adjacent teeth 32 and the upwardly inclined parts of the teeth 33. Such bulging must be resisted-since it can cause depression of the upper surface of the rubber body.

The reinforcing rods also increase the tendency of the rubber body to buckle downwardly. This is because the rubber body tends to actas an I-sectioned'beam, and the rods 51-stiflen the lower flange of this beam.

It will be appreciated that thearrangement is. such thatthe rubber body 21- remains always in compression at the widest dibetween the sections 10 and 11, even The spaces 60 between the edge bars 24 and the flanges 45 of the comb structures are filled with any suitable filling material, e.g. asphalt.

The rubber body 21 and the edge bars 24 are made in lengthwise sections as shown in FIG. 2. The sections are bolted together by means of the edge bars as indicated at 61 in FIG. 2. The reinforcing rods in the rubber of adjacent sections may also be joined end to end as at 62. r

The joint as described may be modified in that the rubber body bulges downwardly across the whole of its under surface 23 throughout the expansion range tending to narrow the expansion gap, the body being .,sup ported by the teeth 32, 33 only in the regions of the rods 51, the rods resting on the inclined'surface parts 41 of the teeth as previously described, but the body remaining at all times clear of the horizontal surface parts 40 of the teeth. In this case (or in any case) an additional reinforcement-may be provided totally embedded in the rubber body and extending lengthwise in its mid longitudinal plane 52.

A modified arrangement as just described may conveniently be adopted in cases where the degree of expansion to be accommodated is quite small. In that event the rubber body does not have to be very wide so that underneath support for the body only in the planes of the rods 51 may be suflicient.

In a still further modification the rubber body may be supported in its mid longitudinal plane and in planes one to each side of its mid longitudinal plane over the whole of the expansion range. Thus the condition indicated in the drawings may be made to correspond to the widest gap dimension to be bridged in the use of the joint.

The present invention provides an expansion joint of simple construction which is readily built without special tools during normal construction work and which ensures that the surface at the joint remains substantially flat and in the plane of the surfaces adjacent the joint over a designed range of ambient temperature conditions. In other words the joint does not, at least to any objectionable extent, form a local bulge or depression in the surface of the roadway. The joint at all times completely fills the space between the adjacent'surfaces, so that water cannot penetrate through the roadway. Drainage means for the joint is therefore unnecessary. Since the rubber body. is always in compression, objectionable tension stresses in the joint are avoided. The rubber body of the joint is adequately supported so that it is not depressed by vehicles which travel over it. As a consequence neither the joint nor the vehicles are subjected to large impact forces.

It is to be noted that the tooth gaps of the comb structures 28, 29 are wider than the teeth 32, 33 in the example described, the teeth being interleaved with clearance on each side. This permits the expansion joint to be set up with one of the comb structures on the skew relative to the other.

This is of considerable advantage since quite often a roadway is required to join with a bridge at a small angle.

1f the joint is required to follow the camber of a roadway this is possible since the joint is made up of relatively short sections and the camber can be accommodated at the junctions of the sections.

We claim:

1. An expansion joint for accommodating the expansion of a pair of surfacing members separated by the joint, the joint bridging an expansion gap between the surfacing members, the joint comprising a body of rubber held always in a state of compression between the surfacing members, said body having a substantially plane upper surface and a thickness in the region of its mid longitudinal plane between the surfacing members which is substantially greater than its thickness in regions adja cent its longitudinal edges whereby the body tends to buckle downwardly under the action of the compressive forces exerted upon it by the surfacing members and support means under the body and supporting the body against downward buckling with its upper surface substantially in the plane of the upper surfaces of the surfacing members, the support means comprising interdigitated elements carried respectively from the two surfacing members so as to be adjustable by expansion of the surfacing members, said elements having oppositely inclined, inter-facing support surfaces for the rubber body 1 which move away from one another upon expansion of the surfacing members to accommodate bulging of the undersurface of the rubber body.

2. An expansion joint as claimed in claim 1, wherein said inter-digitated elements have horizontal support surfaces for the rubber body disposed between said inclined interfacing support surfaces, the horizontal support surfaces supporting the rubber body inits mid longitudinal plane over at least a latter part of the expansion range of the surfacing members.

3. An expansion joint for accommodating the expansion of a pair of surfacing members separated by the joint, the joint bridging an expansion gap between the surfacing members, the joint comprising a body of rubber held always in a state of compression between the surfacing members, said body having a substantially plane upper surface and a thickness in the region of its mid longitudinal plane between the surfacing members which is substantially greater than its thickness in regions adjacent its longitudinal edges whereby the body tends to buckle downwmdly under the compressive forces acting upon it, and a pair of comb structures each having a backbone member with projecting teeth, the comb structures being fixed one to each of the surfacing members with their teeth interleaved and extending in opposite directions across the gap beneath the rubber body, the teeth together defining a trough with inwardly and downwardly inclined sides which move away from one another upon expansion of the surfacing members and vice versa, the inwardly and downwardly inclined sides of the trough supporting the rubber body in planes one to each side of its mid longitudinal plane.

5 v 4. An expansion joint as claimed in claim 3, wherein said teeth havefhorizontal support surfaces for the rubher body disposed in the plane of the floor of the trough and the floor. of the trough supports the rubber body in its. mid longitudinal plane at least over a latter part'of the r 6. An expansion joint as claimed in claim 3, wherein the backbone members of the comb structures together define a trough with inwardly and downwardly inclined side walls, the trough having a flat floor portion adjacent each of its side walls, defined each by a part or of one of the backbone members, and the rubber or like material body has metal edge bars to which it is attached which edge bars are bolted one to each of said floor portions, the edge bans having inclined faces engaging flat against said side walls and holding the rubber body wedged therebetween in a state of compression.

7. An expansion joint as claimed in claim 3, wherein the tooth gaps of the comb structures are wider than the teeth, the teeth being interleaved with clearance on each side.

8. An expansion joint for accommodating the expansion of a pair of surfacing members separated by the joint, the joint bridging an expansion gap between the surfacing members, the joint comprising abody of rubber held'always in a state of compression between the sur-.

facing members, the body having a substantially plane upper surface and atleast one longitudinally extending, metal reinforcement embedded in the body adjacent its faces on the two series of elements being oppositely inclined and facing one another, the support surfaces supporting the rubber body in planes one to each side of its mid longitudinal plane.

9. A bridge expansion joint as claimed in claim 8,

wherein the rubber body has a convex undersurface and two of said metal reinforcements are provided one in each of said planes one to each side of its mid longitudinal plane.

10. An expansion joint for accommodating the expanslon of a pair of surfacing members separated by the joint, the jointbn'dging an expansion gap between the surfacing members, the joint comprising a body of rubber held always in a state of compression between the surfacing members, said body having a substantially plane upper surface and a thickness in the region of its mid longitudinal plane between the surfacing members which is substantially greater than its thickness in regions adjacent its longitudinal edges whereby the body tends to buckle downwardly under the compressive forces acting upon it, a series of support elements carried from one of the surfacing members, a series of support elements carried from the other of the surfacing members, said series of support elements extending respectively in opposite directions across the gap beneath the rubber body in inter-digitated relation, the elements having support surfaces for the rubber body inclined upwardly towards the extremities of the elements, the support surfaces on the two series of elements being oppositely inclined and facr 1 ber body in planes oncto each side of its mid longitudinal-plane; 7 1' I Refrqces Cited by the-Examine UNITED STATES PATENTS 1,978,283. 10/34 Rew 94-'-1s 2,181,018 11/39 .Hughes 94- 18 250303 12/41 'Leg'uillon 94 1s Q 7 U 1 2,254,711 9/41 Bitney 1 .94-18 x 2,351,255 6/44 Fischer "9 1-18 3,018,703 1/62 Fujihara 94 V FOREIGN PATENTS 615,171 2/61 Canada.

J ACOBL. NACKENOFF,'Primary Examiner. 1 WILLIAM I. MUSHAKE, Examiner. 

1. AN EXPANSION JOINT FOR ACCOMMODATING THE EXPANDSION OF A PAIR OF SURFACING MEMBERS SEPARATED BY THE JOINT, THE JOINT BRIDGING AN EXPANSION GAP BETWEN THE SURFACING MEMBERS, THE JOINT COMPRISING A BODY OF RUBBER HELD ALWAYS IN A STATE OF COMPRESSION BETWEEN THE SURFACING MEMBERS, SAID BODY HAVING A SUBSTANTIALLY PLANE UPPER SURFACE AND A THICKNESS IN THE REGION OF ITS MID LONGITUDINALLY PLANE BETWEEN THE SURFACING MEMBERS WHICH IS SUBSTANTIALLY GREATER THAN ITS THICKNESS IN REGIONS ADJACENT ITS LONGITUDIANL EDGES WHEREBY THE BODY TENDS TO BUCKLE DOWNWARDLY UNDER THE ACTION OF THE COMPRESSIVE FORCES EXERTED UPON IT BY THE SURFACING MEMBERS AND SUPPORT MEANS UNDER THE BODY AND SUPPORTING THE BODY AGAINST DOWNWARD BUCKLING WITH ITS UPPER SURFACE SUBSTANTIALLY IN THE PLANE OF THE UPPER SURFACES OF THE SURFACING MEMBERS, THE SUPPOPRT MEANS COMPRISING INTERDIGITATED ELEMENTS CARRIED RESPECTIVELY FROM THE TWO SURFACING MEMBERS SO AS TO BE ADJUSTABLE BY EXPANSION OF THE SURFACING MEMBERS, SAID ELEMENTS HAVING OPPOSITELY INCLINED, INTER-FACING SUPPORT SURFACES FOR THE RUBBER BODY WHICH MOVE AWAY FROM ONE ANOTHER UPON EXPANSION OF THE SURFACING MEMBERS TO ACCOMMODATE BULGING OF THE UNDERSURFACE OF THE RUBBER BODY. 